The present invention generally relates to charging a battery and maintaining battery charge. More particularly, the present invention relates to battery charging and maintenance of battery charge in a power system that is primarily supplied power from an alternating current (AC) generator.
In some electrical power systems of vehicles such as aircraft or other aerospace vehicles, electrical power may be generated with an AC generator and then distributed to various electrical loads through distribution buses. Some loads may be AC loads and may receive power through an AC bus. Other loads may be direct current (DC) loads and may receive power through a DC bus. The DC bus may be provided with power through a transformer/rectifier unit (TRU) which may be connected to the AC bus.
A typical aircraft power system may be provided with one or more batteries which may also supply power to the DC bus. These batteries may be in various states of charge or discharge depending upon factors such as whether or not engine starting has occurred recently (in case of engine or APU electric start) or whether or not the batteries have been used for maintenance. The batteries may extract current from the DC bus at various rates for purposes of charging or maintaining charge. Typically, the batteries are not connected directly to the DC bus from which they receive charging current. They are instead interconnected to the DC bus with an intervening battery charging circuit or battery charger. The battery charger may control current flow to the batteries to assure that the batteries do not become overheated or otherwise damaged during charging.
In some aircraft power systems, the batteries may be connected to the DC bus without use of intervening battery chargers. In these systems, a specialized regulated transformer/rectifier unit (RTRU) may be employed to control voltage on the DC bus at a level that is suitable to assure that battery damage may be precluded during charging. Charging of a battery from a DC bus supplied by un-regulated TRU has heretofore been avoided due to bus voltage variations with amount of load connected to the bus leading therefore to deficient charging.
Dedicated battery chargers and/or specialized RTRU's may add to cost and weight of an aircraft.
As can be seen, there is a need to provide power from an AC generator for battery charging and maintenance of battery charge without use of dedicated battery chargers or specialized RTRU's.